Chuck for shank type tools



United States Patent [72] inventor Karl Seitter Thielenbrucher Allee 36,Cologne-Dellbrueck, Germany [21] Appl. No. 748,104 [22] Filed July 26,1968 [45] Patented Nov. 24, 1970 [32] Priority July 28, 1967 [33]Germany [31] N0.Pl627ll5.1

[54] CHUCK FOR SHANK TYPE TOOLS 9 Claims, 10 Drawing Figs.

[52] U.S. Cl...' 279/51, 74/107 [51] Int.Cl B23b3l/10 [50] FieldofSearch 74/107; 279/51, 43, 46

[56] References Cited UNITED STATES PATENTS 1,530,227 3/1925 Bourassa Q.74/107 FOREIGN PATENTS 309,858 0/1929 England 279/51 PrimaryExaminerRobert C. Riordon Assistant Examiner-Donald D. EvensonAttorney-L0wry, Rinehart, Markva'& Smith ABSTRACT: This disclosureprovides a chuck for shank type tools which has an adapter sleeve and aclamping element. The adapter sleeve engages the shank of the tool beingoperated and is actuated through the use of an eccentric shaft locatedin the chuck housing and in a direction normal to the longitudinal axisof the chuck. A flexible member is placed between the eccentric shaftand the adapter sleeve to provide tensioning for the operation ofthechuck.

Patented Nov. 24, 197 3,542,385

Sheet l of4 FIG. i

KARI. SEITTER Patented Nov. 24, 197% 35%2385 Sheet 2 of 4 INVENTOR KARI.SE/TTER Pa Cnted Nov, 24, 1970 315,5,

Sheet of 4 \\\\\\\\\1X\W I VENTOR Patented Nov. w?

Sheet, of 4 VENTO 1 CHUCKFORSHANKTYPETOOLS BACKGROUND OF THE INVENTIONPrior art chucks used for cylindrical cutter shanks are generallydesigned togrip thetool shank by means of a Iongitudinally slotted andradially flexible adapter sleeve. A clamping element generally actsonthe flexible adapter sleeve in a longitudinal direction. The clampingelement is usually a cap nut acting as a slide screw. By turning the capnut, the flexible adapter sleeve is pushed into-a counter cone therebyexerting a radial clamping force onthe tool shank.

This type of priorart chuck assembly is undesirable for several reasons.The large amount of friction generated between the parts duringtheclamping operation results in a poor working efficiency. This frictioncreated between the thread of the cap nut and the chuck housing andadditional friction resulting dueto-thecontact between the surfaces ofthe adapter sleeve andclamping element result in poor operationalefficiency. The adapter sleeves known in the prior art generally havepoor flexible deformability. This fact increases the total amount offriction contributing to the inefficiencyof the assembly. Thiscombination of difficulties creates a deleterious relationship betweenthe clamping forces and the loosening forces. That is, the clampingforces caused by the twisting movement used to tighten the shank intothe chuck and the rotating movement which causes the tool shank to slipduring use so that when tool shanks are clamped into prior art chuckswith the standard threaded nuts, the clamping and loosening forces aresubstantially identical.The overall efficiency of the normal clampingdevices of those known in the prior art is often below 5 percent.Furthermore, no permanent clamping effect is achieved because there isno flexible member included in the prior art structures.

In another prior art embodiment of'a chuck for shank type tools; thetool shank has a thread located at the clamping end. The shank'isscrewed into a counter thread on the adapter sleeve until a fixed stopon the centralizing bore of the cutter and a fixed point in the body ofthe chuck meet. If the cutter tool slips, the thread and stop forceautomatically retighten the cutter tool. One of the biggestdisadvantages of this type of prior art chuck is that loosening of thetool after use is even more difficult than the normal cap nut type oftool chuck. The powerful axial pressure created on retightening couldeasily lead to the damage of small cutter tool points and tool diametersalong the centralizing bore. In addition, the threading of the end ofthe tool shank increases the total overall production cost for thecutter tools.

SUMMARY OF THE INVENTION The object of this invention is to provide achuck for shank -type tools in which the efficiency of the clamping iscons'iderably increased and the clamping moment is reduced.

Another object of this invention is to provide a chuck having acontacteccentric drive which moves the adapter sleeve in an axial directiononly and prevents any peripheral friction upon tightening and looseningof the adapter sleeve.

- Another object of this invention is to provide an eccentric shaftlocated in a direction normal to the longitudinal axis of the chuck toprovide a' substantially easier operation than prior art standard screwdrive threaded nut means.

'A further object of this invention is to provide an eccentric drive forthe chuck tools to there thereby eliminate screw drive stresses normallyapplied to the gear wheels of milling machines.

A still further object of the invention is to provide a chuck for shanktype tools wherein'there is an improved observation of the work duringuse of the particular cutting-tool.

Another object of this invention is to provide a continuous clampingeffect through the inclusion of a flexible member which acts upon theclamping device.

A still further object of this invention is to provide a chuck forclamping shank type cutting tools requiring a low turning LII , mountedin the chuck housing in a direction normal to the chuck longitudinalaxis. The eccentric shaft acts on the adapter sleeve which is mounted inthe housing and is longitudinally displaceable therein. A flexiblemember may be placed between the eccentric shaft and the adapter sleeveto assist in the longitudinal displacement of the adapter sleeve by theeccentric shaft. The chuck for clamping shank type tools as disclosed inthis invention requires less than one-twentieth of the clamping forcerequired in the standard screw drive prior art chucks. Through the useof the flexible member, a relatively small eccentric lift is sufficientto tighten the chuck. In this invention the eccentric lift may be fromabout 1.5 to 2 mm.

The chuck of this invention is provided with a clamping piece which actson the flexible member. The clamping piece has an oval bore in which theeccentric shaft surrounded by a cylindrical sleeve is mounted. Theeccentric shaft may be mounted within the cylindrical sleeve and chuckhousing through the use of contact bearings such as needle bearings. Therotation of the eccentric shaft within the oval bore through the use ofthe needle bearings contributes to the improvement of the overallefficiency of the chuck because of the elimination of deleteriousfriction losses. The resulting elimination of the deleterious frictionlosses provides additional frictional forces on the tool shank which arefrom about 20 to 25 times greater than those previously obtained onprior art chucks. The bore in the clamping device is oval shaped sothatthe final clamping and loosening position of the eccentric is fixedand secured against any undesired movement.

Further improvement of the clamping effect may be accomplished byinsuring the accurate alinement of the adapter sleeve during rotationwhile under clamping pressure. To accomplish this, a holding sleeve isprovided in the chuck housing adjacent the adapter sleeve. Each of thesleeves has conical surfaces which are in contact and are movable withrespect to each other. Each of the sleeves has a separated structure byvirtue of a continuous longitudinal slot. [Each sleeve may be providedwith notches along the internal and/or external perimeter. The notchesmay extend along the entire length of each sleeve and be separated byfixed narrow legs. In the use of this structure, the legs move intonotches parallel to the sleeve axis and in this way provide easyflexible deformability of the sleeves. The notched, conically shapedsleeves provide an extraordinarily favorable surface connection betweenthe tool shank, clamping sleeves and the main bore of the chuck housing.This particular structure contributes to increased utilization of theclamping force applied to the chuck.

BRIEF DESCRIPTION OF DRAWINGS Other objects of this invention willappear in the following description and appended claims, reference beingmade to the accompanying drawings forming a part of the specificationwherein like reference characters designate corresponding parts in theseveral views.

- In the accompanying drawings, wherein illustrative embodiments of theinvention are disclosed,

FIG. 1 shows a longitudinal section of a chuck made in accordance withthis invention having an adapter sleeve in the clamped position,

FIG. 2 shows a longitudinal sectional view along the line Il-II of FIG.1 with the adapter sleeve in a loosened position.

FIG. 3 is a cross-sectional view along the line Ill-III of FIG. 1,

FIG. 4 shows an enlarged detailed view of the adapter sleeve shown inFIGS. 1 and 2,

FIG. 5 shows a longitudinal sectional view of an eccentric shaft ofachuck made in accordance with this invention,

FIG. 6 is an end view of the said eccentric shaft in the direction VI OFFIG. 5.

as shown in FIGS. 1 and 2, and

FIG. 10 is an end view of the holding a sleeve in the direction X ofFIG. 9.

DESCRIPTION SPECIFIC EMBODIMENT The chuck, generally designated 1, has ahousing 2 with a clamping piece 3 mounted therein. The clamping piece 3engages the said housing 2 by means of a pivot end 3a in a correspondingbore section, and is longitudinally movable within the said housing 2.The clamping piece 3 includes a transverse bore 4. An eccentric shaft 5surrounded by a sleeve 6 is rotatably mounted, within the transversebore 4. Needle bearings 7 are provided between the said shaft 5 andsleeve 6 to reduce friction for. the movement of shaft 5. The shaft 5has an internal hexagonal head 8 at one end thereof. A bushing 9surrounds the other end of shaft 5 within the chuck 1. An innerhexagonal head screw 10 secures the bushing 9 to the conical end of theshaft 5. The eccentric shaft 5 is mounted in the transverse bore 12' ofhousing 2 at the hexagonal head 8 and bushing 9. Needle bearings 11 areplaced between the shaft 5 and transverse bore 12 to facilitate movementbetween these parts. The shaft 5 has an eccentric cylinder body portion511 having an eccentric axis 13. The eccentric axis 13 is parallel tothe longitudinal axis 14 of the shaft 5 shown passing through the innerhexagonal head 8 in FIG. 5. The transverse bore 4 is kept horizontallyoval so that the recess 4a is formed alongside the circular sleeve 6.Eccentricity of the recess 4a is about 0.3 mm. and comparable with axesl3 and 14.

A threaded shoulder 3b is located at the lower end of the clamping piece3. An inner hexagonal nut 15 is screwed onto the threaded shoulder 3b. Aflexible member, cup springs 16 in this embodiment, is located on thecylindrical external diameter of the hexagonal nut 15. The cup springs16 are pretensioned between the surfaces of the clamping piece 3 and theadapter sleeve 17 The tensioning of the cup springs 16 is effected bythe movement of the inner hexagonal nut 15. The amount of tensioning inthe specific embodiment is about one-half the permissible maximumtension available. The tool shank 18 is inserted into the adapter sleeve17. The adapter sleeve 17 has a conical external periphery wherein theconical surface narrows as it approaches the tool having the tool shank18. The cutters which are normally right hand spiral tighten up moresecurely by means of the ensuing axial force through the use of such anadapter sleeve 17.

The holding sleeve 19 provides several advantages. First, it is possibleto use the tension of the cup springs 16 to the fullest advantage.Secondly, the changing of the adapter sleeve 17 is made easier.Furthermore, the holding sleeve 19 provides compensation for thediameter tolerances of the tool shank l8 and the various clampingelements. The holding sleeve 19 is designed just like the adapter sleeve17 so that it fills the bore 20 of the chuck housing 2 thereby beingaccurately in rotation with the adapter sleeve 17 and tool shank 18. Theholding sleeve 19 includes a threaded portion 19a for screwing into thehousing 2 facilitating an axial adjustment. The axial adjustment ofsleeve 19 provides for the compensation of manufacturing tolerances inthe chuck 1 and tool shank 18. In addition, the adjustability providesfor a predetermined clamping force in accordance with a fixed oradjustable scale on the visible side of the sleeve 19 or at the lowerend of the chuck body 2.

The conical shape of one-tenth on adapter sleeve 17 and holding sleeve19 lies in the nonreversibility range. This shape characteristicprovides automatic withdrawal of the adapter sleeve 17. The internalhexagonal nut 15 which is secured to the clamping piece 3 has anexternal collar 15a. The adapter sleeve 17 has a correspondingprojecting shoulder 17a. The collar 15a of the inner hexagonal nut 15fits the shoulder 17a Notches 17 c and 17d are located along the outerperiphery and inner periphery, respectively, of the inner bore of theadapter sleeve 17'. The notched structure includes narrow legs 17e whichgive the adapter sleeve 17 a unified structure. There are eleven notches17c and 17d along the outer and inner surfaces, respectively, of theadapter sleeve 17 thereby providing an effective means for flexiblydeforming the said sleeve 17. A collar 17f located on the inner surfaceof the adapter sleeve I7 limits the movement of the tool shank I8 intothe adapter sleeve 17.

The holding sleeve 19 also has a continuous longitudinal slot 22 whichdivides the holding sleeve 19 along one side. The holding sleeve 19includes notches 1% which extend the whole length of the holding sleeve19 along its inside surface. A further embodiment of the holding sleeve19 could also include notches along the outside surface thereof such asare provided on the outside surface of the adapter sleeve 17. Theholding sleeve 19 includes grooves 19c which run cruciform and serve totake a key for the adjustment of the holding sleeve 19 within the bore20 ofthe housing 2.

In operation, the eccentric shaft 5, 5a of the chuck l is first turnedto the left by inserting a two-ended inner hexagonal key into the innerhexagonal head 8. The shaft 5, 5a is placed in an upper end position asseen in FIG. 2. The resultant upward movement of the clamping piece 3causes the cup springs 16 to be tensioned to a point determined by thelocation of inner hexagonal head 15 on the pivot end 30. The tool shankI8 is then guided into the adapter sleeve 17. The eccentric shank 5, 5ais then turned in a CiOCk' lSC direction within the sleeve 6 by way ofthe needle bearings 7. The sleeve 6 hobs in the oval bore 4, 4a andpushes the clamping piece 3 downward thereby pressing onto the topsurface of the adapter sleeve 17 through the tensioned cup springs 16.This adapter sleeve 17 is thus gradually pressed into the cone of theholding sleeve 19 until the clamping force on the tool shank 18 reachesthe desired amount. This clamping force is applied on the conicalsurfaces of the adapter sleeve 17 and the holding sleeve 19 and alongthe cylindrical surface between the holding sleeve 19 and the bore 20 ofthe housing 2. Experience has shown that the ratio of the clampingmoments to loosening moments can be improved from 1:1 1:1 to about 1:20to 1:25 with the clamping device of this invention. The eccentric shaft5, 5a can be turned about 200. After turning this far, the eccentricmidpiece 5a locates a stop about 10 behind the highest clamping positionwithin the oval bore 4, 4a. This stop limits turning to the right andblocks inadvertent turning to the left with the aid of the cup springs16. The springs 16 are tensioned to about one-half of the maximumtension in this embodiment. To loosen the chuck l, the eccentric shaft5, 5a is turned counterclockwise. The counterclockwise turning of theshaft 5, 5a causes the clamping piece 3 to be withdrawn together withthe inner hexagonal nut 15 until the collar 15a and shoulder 17a meet.The withdrawal of the clamping piece 3 releases the springs 16 to theamount of its pretensioning. With further withdrawal of the clampingpiece 3, the collar 15 pulls over the shoulder 170. At the same time,the inner diameter of the adapter sleeve 17 is increased by the radialcomponents on the collars 15a and the shoulder 17a so that tool changingmay be easily made possible.

While the chuck for shank type tools has been shown and described indetail, it is obvious that this invention is not to be considered asbeing limited to the exact form disclosed, and that changes in detailandconstruction may be made therein within the scope of what is claimed,without departing from the spirit of this invention.

l claim:

1. A chuck for shank type tools comprising, in combination:

a. a chuck housing;

b. means mounting a clamping element within said housing;

c. means connecting a radially displaceable adapted sleeve means to saidclamping element;

d. said clamping element including an eccentric shaft mounted in saidhousing and having an axis located in a direction normal to thelongitudinal axis of the said chuck; e

. a flexible member interposed between the eccentric shaft and theadapter sleeve means within said chuck housing; and

f. means to rotate said eccentric shaft to effect the longitudinaldisplacement of said clamping element to cause the opening and closingof the said adapter sleeve means around a tool shank. 2. A chuck asdefined in claim 1 wherein said flexible member is a set of cup-springs.

centric shaft and said chuck housing.

5. A chuck as defined in claim 1 including:

means mounting a longitudinally displaceable holding sleeve havingacounter cone surface within said housing juxtaposed the adapter sleevemeans; and

the said adapter sleeve means having a conical shape which narrows in adirection away from the chuck housing.

6. A chuck as defined in claim 5 wherein:

said adapter sleeve means includes a shoulder portion and said clampingelement includes a collar portion; and 'said shoulder and collarportions being located with respect to each other to engage during thewithdrawal of said adapter sleeve means to provide locking between therespective parts. A chuck as defined in claim 6 wherein said adaptersleeve means includes a continuous slot completely through itsstructure' along its entire length and notches along at least one of theinner and outer surfaces of said adapter sleeve.

8. A chuck as defined in claim 7 wherein said holding sleeve includes acontinuous slot completely through its structure and along its entirelength and notches along at least one of the inner and outer surfaces ofsaid holding sleeve.

9. A chuck as defined in claim 3 wherein the eccentric surface of saideccentric shaft and said sleeve member extend between opposite sides ofsaid clamping element whereby upon rotation said eccentric shaft applieseven pressure across the entire width of said clamping element.

